A standard ball-type conveyor such as described in U.S. Pat. No. 4,681,221, issued July 21, 1987, has a stationary support frame and a plate on the support frame formed with a plurality of generally parallel rows of holes extending transversely of a longitudinal transport direction. Underneath each row of balls is a respective shaft that is journaled in the support frame for rotation about a respective transverse axis. Balls in the holes each project upward through the respective hole beyond the plate and downward through the respective hole into engagement with the shaft of the respective row. The shafts can be rotated about the respective axes so as to rotate the balls to displace an object resting on the balls in the longitudinal transport direction.
Such a conveyor has certain advantages over a standard roller conveyor because it supports the load at a plurality of longitudinally and transversely spaced points rather than at a plurality of longitudinally spaced lines. The main difficulty with such devices is, however, that they cannot be used to align the object being conveyed with the longitudinal direction. When, for instance, a heavy object is laterally offset or skewed to the longitudinal direction so that it could catch on the edge of a passthrough opening, it is necessary to laboriously lift the object and reposition it, something that is impossible with large objects like air-freight containers. When the object is large a special orienting crane must be employed.
It has been suggested in German patent document No. 2,261,936 to support the balls not on cylindrical shafts but on flat support surfaces that can be moved somewhat transversely as well as longitudinally. The resultant equipment does allow some degree of position adjustment of the object being conveyed, but is extremely complex and expensive to manufacture and maintain. While it is possible to rotate the object being conveyed through as much as 90.degree., the cost of the equipment is so great as to preclude its widespread use.
In another arrangement a short run of the conveyor can be displaced transversely of a straight-motion takeoff conveyor. This makes it possible to swing the conveyor to one side or the other from a longitudinal centerline so as to allow a canted object to be deposited on the takeoff conveyor extending perfectly longitudinal. Such a piece of equipment needs considerable floor space, making it impossible to use it in an arrangement where the conveyor is sunk in the floor, and as a result of the side-to-side action this equipment is extremely hazardous for operating personnel who might get caught between the device and adjacent equipment.